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authorWill Deacon <will.deacon@arm.com>2017-12-06 10:51:12 +0000
committerWill Deacon <will.deacon@arm.com>2017-12-06 18:28:10 +0000
commitd96cc49bff5a7735576cc6f6f111f875d101cec8 (patch)
tree414b9a833517440b52162e784b3c0ddd96ad6915 /arch
parent0adbdfde8cfc9415aeed2a4955d2d17b3bd9bf13 (diff)
arm64: SW PAN: Update saved ttbr0 value on enter_lazy_tlb
enter_lazy_tlb is called when a kernel thread rides on the back of another mm, due to a context switch or an explicit call to unuse_mm where a call to switch_mm is elided. In these cases, it's important to keep the saved ttbr value up to date with the active mm, otherwise we can end up with a stale value which points to a potentially freed page table. This patch implements enter_lazy_tlb for arm64, so that the saved ttbr0 is kept up-to-date with the active mm for kernel threads. Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Vinayak Menon <vinmenon@codeaurora.org> Cc: <stable@vger.kernel.org> Fixes: 39bc88e5e38e9b21 ("arm64: Disable TTBR0_EL1 during normal kernel execution") Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Vinayak Menon <vinmenon@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/include/asm/mmu_context.h24
1 files changed, 10 insertions, 14 deletions
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index f7773f90546e..9d155fa9a507 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -156,20 +156,6 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu);
#define init_new_context(tsk,mm) ({ atomic64_set(&(mm)->context.id, 0); 0; })
-/*
- * This is called when "tsk" is about to enter lazy TLB mode.
- *
- * mm: describes the currently active mm context
- * tsk: task which is entering lazy tlb
- * cpu: cpu number which is entering lazy tlb
- *
- * tsk->mm will be NULL
- */
-static inline void
-enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
-{
-}
-
#ifdef CONFIG_ARM64_SW_TTBR0_PAN
static inline void update_saved_ttbr0(struct task_struct *tsk,
struct mm_struct *mm)
@@ -193,6 +179,16 @@ static inline void update_saved_ttbr0(struct task_struct *tsk,
}
#endif
+static inline void
+enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
+{
+ /*
+ * We don't actually care about the ttbr0 mapping, so point it at the
+ * zero page.
+ */
+ update_saved_ttbr0(tsk, &init_mm);
+}
+
static inline void __switch_mm(struct mm_struct *next)
{
unsigned int cpu = smp_processor_id();